Nanocrystalline diamond films for mechanical applications
Nanocrystalline diamond films for mechanical applications
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DOI：
10.1002/pssa.200405173
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发表时间：
2004-09
期刊：
影响因子：
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通讯作者：
F. H. Guillén;K. Janischowsky;W. Ebert;E. Kohn
中科院分区：
文献类型：
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作者：
F. H. Guillén;K. Janischowsky;W. Ebert;E. Kohn
纳米晶金刚石薄膜已在热丝 CVD (HFCVD) 系统中生长，允许在 4 硅 (100) 上进行金刚石的 BEN、纹理生长和 HOD 生长。这里讨论的纳米晶金刚石的生长过程包括在硅上进行金刚石成核的BEN过程，整个晶片表面的密度超过10 10 cm -2 。纳米晶金刚石膜的后续生长是通过将氮添加到气相中来实现的，氮与碳的相对浓度为1:1。在 680 °C 至 740 °C 之间的基底温度下，生长厚度在 1 pm 至 20 pm 之间的封闭金刚石薄膜。在低氮浓度下，纳米晶金刚石薄膜仍然呈现柱状结构，横向晶粒尺寸低于200纳米，而垂直晶粒尺寸可以达到几微米。较高的氮浓度导致纳米晶金刚石生长模式没有柱状结构，并且 SEM 无法再检测到晶粒尺寸。金刚石在MEMS技术中的优势依赖于其出色的机械和热性能。此外，还必须考虑由于热膨胀以及薄膜的多晶性质而导致的金刚石薄膜内部的应力分布。通过应用不同的测试结构，我们可以测量这些纳米晶薄膜的断裂强度超过 4.0 GPa，弹性模量高达 1020 GPa。在大多数情况下，固有的垂直和水平应力保持在 5 MPa 的检测极限以下，因此可以制造长度为几毫米的独立式结构，而不会出现明显的弯曲。
Nanocrystalline diamond films have been grown in a hot filament CVD (HFCVD) system allowing BEN, textured growth and HOD growth of diamond on 4 silicon (100). The growth process of nanocrystalline diamond discussed here consists of a BEN process for diamond nucleation on silicon, with a density of more than 10 10 cm -2 across the entire wafer surface. The subsequent growth of the nanocrystalline diamond films is achieved by addition of nitrogen into the gas phase with a relative concentration to carbon of 1:1. At substrate temperatures between 680 °C and 740 °C, closed diamond films are grown with thicknesses between 1 pm and 20 pm. At low nitrogen concentrations the nanocrystalline diamond films exhibit still a columnar structure with a lateral grain size below 200 nm whereas the vertical grain size can reach several microns. Higher nitrogen concentrations lead to a nanocrystalline diamond growth mode with no columnar structure and a grain size is no longer detectable by SEM. The advantages of diamond in MEMS technology rely on its outstanding mechanical and thermal properties. Additionally, the stress distribution inside the diamond films due to thermal expansion as well as the polycrystalline nature of the film has to be taken into account. Applying different test structures we could measure fracture strength of more than 4.0 GPa and elasticity moduli of up to 1020 GPa for these nanocrystalline films. The intrinsic vertical and horizontal stress remains in most cases below the detection limit of 5 MPa, so that freestanding structures with a length of several millimeters can be fabricated without noticeable bending.